P8. Forces In Balance

Question 1

What is a vector?

Answer 1

Physical quantitis with size (magnitude) AND direction

Question 2

What is a scalar?

Answer 2

Physical quantities with size (magnitude) but no direction

Question 3

What is mass and weight?

Answer 3

Mass= Amount of matter (does not change)
Weight= force of gravity on mass

Question 4

Give 4 examples of vector quantities

Answer 4

• Acceleration
• Force
• Weight
• Velocity

Question 5

Give 4 examples of scalar quantities

Answer 5

• Speed
• Time
• Distance
• Power
• Energy
• Mass

Question 6

What os the difference between distance and displacement?

Answer 6

Distance is how far something is whilst taking multiple directions whilst displacement is the distance between a start and end point in a singular direction.

Question 7

What is the difference between speed and velocity?

Answer 7

Speed is how quickly something moves but not in a certain direction (scaler). Velocity is the speed of something moving in a singular direction (vector).

Question 8

What does the length of the arrow show in a diagram?

Answer 8

Size (magnitude)

Question 9

What is the difference between contact and non-contact forces?

Answer 9

Contact forces are forces that require direct physical contact between two objects. Non-contact forces are forces that act on an object without the need for physical contact.

Question 10

Give three examples for contact forces

Answer 10

• Air resistance
• Tension
• Friction

Question 11

Give three examples for non-contact forces

Answer 11

• Magnetic
• Electrostatic
• Gravitational
• Thrust

Question 12

What is the Newton’s third law of motion?

Answer 12

For every action, there is an equal opposite reaction

Question 13

What is the definition of friction?

Answer 13

Friction is the force exerted by a surface as an object moves across it

Question 14

What is thrust?

Answer 14

A forwards force

Question 15

What is the reaction force

Answer 15

It stops things from going right through solid objects. When this force acts from your chair it pushes you upwards so that you do not fall through it.

Question 16

What is the resultant force?

Answer 16

The resultant force a singular force on an object that has the same effect as all of the forces acting on the object. You get this when you subtract the smaller force from the larger force acting on the object. For example, if air resistance is 800N snd weight is 800N, the result force will be 0N, causing them to move at a consistent speed.

Question 17

What is a balanced force?

Answer 17

Two forces that have the same size but opposite directions, causing something to move at a constant velocity and direction or remain still; no acceleration or decceleration.
Resultant force: 0N

Question 18

What is an unbalanced force?

Answer 18

An unbalanced force is when two forces moving in opposite directions act on a singular object and one of the forces is greater than the other.

Question 19

What is terminal velocity?

Answer 19

Ahen all forces are balanced so the speed becomes constant

Question 20

What is a moment?

Answer 20

The moment is the turning force around a fixed pivot.
Moment = NeutonMeters (NM)
Moment = Force x Perpendicular Distance

Question 21

How can you increase a moment?

Answer 21

• Increase the force applied
• Increase the perpendicular distance from the pivot

Question 22

What is the distance of a moment?

Answer 22

The distance from the pivot to the line of action of the force

Question 23

Would the moment be larger of you use a longer spanner?

Answer 23

M=FxD, so if the distance increases, M will also increase

Question 24

What are force multipliers?

Answer 24

Force multipliers multiply the applied force, allowing you to lift more for less work. The applied force is always further from the pivot than the force you’re trying to overcome

Question 25

What is the use of gears?

Answer 25

Gears are used to change the moment of a turning effect

Question 26

How do you work out the moment of a gear?

Answer 26

Moment= Force x Gear radius Example: A gear of radius 15mm turns with a force of 100N. What is the moment produced by the gear? 100N x 0.015m = 1.5Nm

Question 27

How do you calculate the gear ratio?

Answer 27

Number of teeth on the driven/ number of teeth on the driver

Question 28

How do you increase speed using gears?

Answer 28

Using a higher gear

Question 29

What does the gear ratio show?

Answer 29

How many times one gear has to rotate for another gear to complete one full rotation.

Question 30

What is the centre of mass?

Answer 30

The point at which all the object's mass is concentrated

Question 31

How do you find the center of mass in a regualr object?

Answer 31

Draw all lines of symetry and find the point where all lines meet

Question 32

How do you find the center of mass in an irregular object?

Answer 32

1- Suspend the irregular object freely in the air with a plum line connected to the same point 2- Draw a line where the plum line passes as the center of mass lies somewhere on this line, exactly below the point where the object is hung 3- Rotate the object and draw another line where the plum line passes. The point where the two lines meet is the centre of mass

Question 33

When will an object topple over?

Answer 33

When the line of action (beggining at the centre of mass) moves outside the object's base

Question 34

How can a vehicle be redesigned to be made more stable?

Answer 34

The vehicle could be redesigned to be made more stable by lowering the center of mass and making the wheelbase wider

Question 35

Explain why the vehicle does not roll over on this angled embankment.

Answer 35

The vehicle's line of centre of mass is within the base of the vehicle, meaning it will remain upright, until the centre of mass is outside the base, therefore there is no resultant moment.

Question 36

What is the principle of moments and how is it worked out?

Answer 36

This states that, for an object that is not turning: The sum of all the clockwise moments about any point = The sum of all the anticlockwise moments about that point

Question 37

What is a resultant force?

Answer 37

A single force that has the same effect as all the firces acting on the object

Question 38

What are the two possible senarios when the resultant force on an object is 0?

Answer 38

No movement or constant speed with no acceleration or deceleration

Question 39

How do you find the resultant force using the parallelogram of forces

Answer 39

Step 1: Work out a scale Step 2: Copy out one force – The length needs to be draw to scale. Step 3: Measure the angle Step 4: Draw the next force Step 5: Set your compass to the size of one of the forces. Step 6: Place the compass point at the end of the other force and draw an arc. Step 7: Set your compass to the size of the other force. Step 8: Place the compass at the end of the other force and draw a second arc. Step 9: Draw the resultant force from the ship to the point where the two arcs cross. Step 10: Using a ruler measure the size of the resultant force. Step 11: Calculate the size of the resultant force.

Question 40

How do you find the vertical and horizontal components of a diagonal force?

Answer 40

1. Create a scale 2. Measure the angle of the line and then draw the line to scale 3. Draw a horizontal and verticle line meeting at the bottom of the arrow 4. Draw a dotted line horizontally and vertically from the end of the arrow, 90° to the horizontal and vertical lines. 5. Measure how long each line is 6. Calculate the force of the horizontal and vertical compontants using the scale

Question 41

How can we work out hte size of the frictional force to maintain an equilibrium?

Answer 41

* First we can draw a geometric ‘scaled’ free body diagram with our weight acting straight down to ground. * Draw the force acting normal to the slope and the force acting along side/parallel to the slope to form parallelogram. * Measuring FN and FH will give use their magnitude and we can also get their angle easily.